Topic: 'Kin Luna...made of eggshells?

I put my Luna down on the hill today and the fuz is now cracked and the left elev is damaged.
It wasn't a hard landing but having caught a large tuft of grass, i reckon the tailplane instigated a twisting action on the fuz causing damage where the wing stopped the twisting motion (at the rear of the wing seat)...
I can repair it, but narked that I'm having to at such a gentle arrival...maybe I need a carbon DS plane or a splinter...

Sorry to hear it BG - sometimes you get lucky and sometimes you don't mate.

But yes, EVERYONE needs a Splinter!!

Z

Ouch, sorry to hear that BG............... 

Seems to me there isn't much of a happy medium, it's either slap it in foam or cotton wool landing stuff.

I'm still in chicken out mode, and flying foam only............. 

That's a bummer ..

But, that sounds very unusual as well.  Mouldies aren't usually that fragile at all.   Have a look at some videos of F3j landings, and you'll see what I mean:  those guys spear their 3.5 - 3.7 m moulded planes right into the turf in order to get good landing points .  OK, a Luna isn't a mega-buck F3J plane, but still ..

its not exactly going to be a greaser  if the tail plane half is damaged though thats got to be at least 2 inches off the deck

I reckon i can repair it next week with epoxy, a balloon of hot water and cyano, but i dunno about getting the paint job to match...maybe I'll get a carbon mouldie next time...Flying Fish/Blade/Bird...(should have the funds next week )

Even on carbon mouldies the fuses tend to be glass so wouldnt have helped much in this instance  

I wouldnt worry too much about colour match, make a solid repair, blow it over with something close to the colour and enjoy it, you'll fly it more and harder now its not pristine 

Even on carbon mouldies the fuses tend to be glass so wouldnt have helped much in this instance 

harumph...a v-tail wouldn't have done this to the fuz...i reckon i was just VERY unlucky today. I'm the first to admit it when I plonker it up, but today...I honestly can't blame myself.
i bought it to fly it, and these things happen...tch :(

Even on carbon mouldies the fuses tend to be glass so wouldnt have helped much in this instance  

I wouldnt worry too much about colour match, make a solid repair, blow it over with something close to the colour and enjoy it, you'll fly it more and harder now its not pristine 

Not with the carbon Bird according to T9s pictures..l.

It says reinforced but your Luna will probably have carbon reinforcement aswell, wether the Bird fuse it all carbon I don't know but I'm sure Mr Ed could tell you as he has more Birds than T9 

Like you said you were probably just a bit unfortunate but carbon doesnt mean it wont break.

Well i'm gettin' a Flying Fish shortly and we'll see how that one fares

At least my Fillip 400 (which i've repaired) flies like a dream and kept my spirits up today.

I'll try and post some pics for you all to laugh at  

My Birds have had terrible abuse and come up smiling. Today I landed out with my Brio.  No damages.  I think the two metre class is probably the hardest to design. People wan t light wing performance and mouldie build. I' m not too sad my Luna went back.

My Birds have had terrible abuse and come up smiling. Today I landed out with my Brio.  No damages.  I think the two metre class is probably the hardest to design. People wan t light wing performance and mouldie build. I' m not too sad my Luna went back.

So you'd recommend a 60" Bird..is yours carbon?

So you'd recommend a 60" Bird..is yours carbon?

Yes, they're all carbon BUT they don't do what a Luna will do in the way of light stuff. I love the Bird but if it's a Luna replacement you looking for I'd suggest a Typhoon but order a carbon layup. 

i doubt the tailplane could exert much force on to the wing. they are fairly floppy things.

sorry to hear that Bustagrunt. Did you make the existing fuz cutout larger? (the one for the servo leads to go through). This can weaken the fuz by the wing seat!

i doubt the tailplane could exert much force on to the wing. they are fairly floppy things.

The wing seat hweld fine, the tailplane on mine is a firm affair, and the twisting action is what i reckon did the damage.

I've had another look this a,.m. and having removed the nose (thank goodness i used crappy 5 min epoxy), I can stick a layer of glass over the cracks on the inside and soak cyano and then filler from the outside.

I'll be back in the air in a week or two

sorry to hear that Bustagrunt. Did you make the existing fuz cutout larger? (the one for the servo leads to go through). This can weaken the fuz by the wing seat!

only very slightly and no damage there

must have been sliding along at some lick to do damage, your crows should allow you to bring it to a near stop in most winds it'll fly in.
just remember to put them away just before you touch down
only time i damaged mine it came down HARD! and even then it was just a crack around my huge wing seat cut out, now sorted

Carbon isn't all it's cracked up to be I reckon.  It's one big advantage is it's stiff.  Apart from that, it has mainly disadvantages.  It shatters easily.  It's heavy.  It's radio unfriendly. 

Some carbon planes are stronger because they're bleedin' heavy.  But if you make a carbon plane the same weight as a glass plane, it will be a lot stiffer, but it will probably crack/shatter easier.  At equal weights (ie the carbon one would be a thinner skin) carbon cracks easier than glass.

Kevlar won't crack/shatter/break.  But it's bendy.  So the toughest plane will be a mix of kevlar and carbon, or maybe kevlar/carbon/glass.  I wish more planes were made like that, with a weave that had a glass strand, then a carbon strand, then a kevlar strand and so on repeatedly.  That would be one hard to break mouldie.

Carbon isn't all it's cracked up to be I reckon.  It's one big advantage is it's stiff.  Apart from that, it has mainly disadvantages.  It shatters easily.  It's heavy.  It's radio unfriendly.  

Some carbon planes are stronger because they're bleedin' heavy.  But if you make a carbon plane the same weight as a glass plane, it will be a lot stiffer, but it will probably crack/shatter easier.  At equal weights (ie the carbon one would be a thinner skin) carbon cracks easier than glass.

Kevlar won't crack/shatter/break.  But it's bendy.  So the toughest plane will be a mix of kevlar and carbon, or maybe kevlar/carbon/glass.  I wish more planes were made like that, with a weave that had a glass strand, then a carbon strand, then a kevlar strand and so on repeatedly.  That would be one hard to break mouldie.

That seems to be exactly what my Carbon Bird Fuz is....

Sorry to hear of your incident Buster.

I much prefer V - tails to conventionals as they are less prone to landing incidents IMHO, but also I prefer the look!

I also had a small incident yesterday when my Erwin had a slight coming together with a Mini Dragon. Always dodgy scratching for lift in the same thermal. Both recovered and flew on but on landing the erwin has a slight mark on the LE, while the MD was missing a cleanly sliced off wing tip.

I love my Erwin, 2m, all carbon and much repaired

Tim

As I said previously 'cracked *rse' , you cornish loon...i was'nt doing hardly any speed and just tickled it back to the slope as the wind had died as soon as i launched it off the hill.
No Crow required because it was already below my launch position...just one of those unluicky things I guess

Carbon isn't all it's cracked up to be I reckon.  It's one big advantage is it's stiff.  Apart from that, it has mainly disadvantages.  It shatters easily.  It's heavy.  It's radio unfriendly. 

Some carbon planes are stronger because they're bleedin' heavy.  But if you make a carbon plane the same weight as a glass plane, it will be a lot stiffer, but it will probably crack/shatter easier.  At equal weights (ie the carbon one would be a thinner skin) carbon cracks easier than glass.

Kevlar won't crack/shatter/break.  But it's bendy.  So the toughest plane will be a mix of kevlar and carbon, or maybe kevlar/carbon/glass.  I wish more planes were made like that, with a weave that had a glass strand, then a carbon strand, then a kevlar strand and so on repeatedly.  That would be one hard to break mouldie.

Unfortunately it doesn't work quite that way mate. The model is only as strong as the stiffest component of the composite. So if you have a carbon glass layup, the glass will not add any strength to the carbon because it is not as stiff. The carbon strands will break first as they are stiffer. Then the kevlar wouldn't help the glass much as that is in turn more flexible than the glass.

The reason why kevlar gets used in fuses along with carbon or glass, as far as I understand it, is to provide some damping to any high speed vibration that you might get when the boom bends, and then oscillates as a consequence.

It's like cooking - you can't just throw in ALL the flavours that you like all in one dish! It won't turn out as nice as the sum of its parts!

Zim

what if you add 3 parts glass, let to set, then gradually mix in 2 parts carbon (turn the heat down and let it cook for 30 mins on a low hob setting, then fold in some kevlar and bake at 150c(gas 5) for 1 hour. Should make a lovely glider for all the family!

Some RAF military establishment did tests and found that the toughest mix for real planes was carbon on the inside with kevlar on the outside (on both sides).  The kevlar holds the carbon in and prevents the carbon shattering.  But I guess a three-ply construction would be too heavy for models unfortunately.

Sounds like that includes guarding against stuff hitting it!

Yes ... including, in our case, the ground ...

Better to build models to perform, not build them to crash I reckon mate  having said that there are some cool ideas like the attachment of the Erwin wing which really doesn't seem to have a downside.

unless it's raining, really damp, or you've left your tape at home

Will be picking my luna up from the PO tomorrow, you'll soon know how strong they are as the Doc doesnt have a great track record with gliders of the moulded veriety 

I doubt she'll see the winter out, and will be very lucky to see the autumn out...

CM

Zim, the sellotape-on-wing of the Erwin has always annoyed me, trying to wind on the tape in the wind on damp grass ... but today I crashed the Erwin and the sellotape broke and the plane was unscathed, amazing ... so I'm appreciating the sellotape more now ...

RE. the previous discussion on fabrics/fibres, you DO get carbon/kevlar interwoven fabric, but the only ones I've seen have been a bit too heavy for model plane use...

RE. the previous discussion on fabrics/fibres, you DO get carbon/kevlar interwoven fabric, but the only ones I've seen have been a bit too heavy for model plane use...

Inside my Brio E (Brio is the same)



The much tentpegged original Bird I learnt on:



The real repair is to the wing saddle, the fuse flexed and the carbon cracked BUT the kevlar held it together and CA wicked in another patch inside made it stiff again. (ooh err Vicar....)

Love that black/gold combo (Mike Evans?)...

Love that black/gold combo (Mike Evans?)...

Sure gotta love that Black Gold

yep have too agree cant beat  old gold and black

Yep, I reckon next time I buy a quality mouldie I'll go for that carbon/kevlar mix like the above pics of the Brio and Bird. 

Right then...plagiarising genius at work. ...(thanks Tony Fu)...with a 'non concepting' twist...

I went to the local shops and bought...

1. 1 x inner tube..(actually got a punctured one from the bike shop for free)  
2. A packet of condoms...

I then cut the inner tube into a 16" length with the valve attached.
I then folded and glued the ends over then used strapping tape to secure them.

I mixed up some skinning epoxy and glassed a portion of wing bandage over the cracks in the inside


I then put the condom over the inner tube (as a release agent) and to make sure the inner tube doesn't stick to the inside of the fuz .
I then inserted (oooer missus) the tube/condom combo into the fuz and inflated the tube

Leave to harden and then hopefully tomorrow it'll be as good as repaired , although I might put a second bandage in place


i'd post pics, but google chrome seems to have changed my settings for posting pics

LoL
Buster's repaired Luna fuz after inflation..................

LoL
Buster's repaired Luna fuz after inflation..................

Lol !

"Give it one more pump!"

"OK!"

BOOM!